Redox‐Sensitive Stomatocyte Nanomotors: Destruction and Drug Release in the Presence of Glutathione

The development of artificial nanomotor systems that are stimuli‐responsive is still posing many challenges. Herein, we demonstrate the self‐assembly of a redox‐responsive stomatocyte nanomotor system, which can be used for triggered drug release under biological reducing conditions. The redox sensitivity was introduced by incorporating a disulfide bridge between the hydrophilic poly(ethylene glycol) block and the hydrophobic polystyrene block. When incubated with the endogenous reducing agent glutathione at a concentration comparable to that within cells, the external PEG shells of these stimuli‐responsive nanomotors are cleaved. The specific bowl‐shaped stomatocytes aggregate after the treatment with glutathione, leading to the loss of motion and triggered drug release. These novel redox‐responsive nanomotors can not only be used for remote transport but also for drug delivery, which is promising for future biomedical applications.     

Thiol-Ene Cationic and Radical Reactions: Cyclization,Step-Growth,and Concurrent Polymerizations for Thioacetal and Thioether Units

Thiol-ene cationic and radical reactions were conducted for 1:1 addition between a thiol and vinyl ether, and also for cyclization and step-growth polymerization between a dithiol and divinyl ether. p-Toluenesulfonic acid (PTSA) induced a cationic thiol-ene reaction to generate a thioacetal in high yield, whereas 2,2′-azobisisobutyronitrile resulted in a radical thiol-ene reaction to give a thioether, also in high yield. The cationic and radical addition reactions between a dithiol and divinyl ether with oxyethylene units yielded amorphous poly(thioacetal)s and crystalline poly(thioether)s, respectively. Under high-dilution conditions, the cationic and radical reactions resulted in 16- and 18-membered cyclic thioacetal and thioether products, respectively. Furthermore, concurrent cationic and radical step-growth polymerizations were realized using PTSA under UV irradiation to produce polymers having both thioacetal and thioether linkages in the main chain.     

Linear‐Dendritic Alternating Copolymers

Herein, the design, synthesis, and characterization of an unprecedented copolymer consisting of alternating linear and dendritic segments is described. First, a 4th‐generation Hawker‐type dendron with two azide groups was synthesized, followed by a step‐growth azide‐alkyne “click” reaction between the 4th‐generation diazido dendron and poly(ethylene glycol) diacetylene to create the target polymers. Unequal reactivity of the functional groups was observed in the step‐growth polymerization. The resulting copolymers, with alternating hydrophilic linear and hydrophobic dendritic segments, can spontaneously associate into a unique type of microphase‐segregated nanorods in water.     

Co-syndiospecific Alternating Copolymerization of Functionalized Propylenes and Styrene by Rare-Earth Catalysts

The precise control of monomer sequence and stereochemistry in copolymerization is of much interest and importance for the synthesis of functional polymers, but studies toward this goal have met with only limited success to date. Now, the co-syndiospecific alternating copolymerization of methoxyphenyl- and N,N-dimethylaminophenyl-functionalized propylenes with styrene by half-sandwich rare-earth catalysts is reported. This reaction efficiently afforded the corresponding functionalized propylene-alt-styrene copolymers with a perfect alternating sequence and excellent co-syndiotacticity (rrrr >99 %), thus constituting the first example of co-stereospecific alternating copolymerization of polar and non-polar olefins.     

Unprecedented Sequence Control and Sequence-Driven Properties in a Series of AB-Alternating Copolymers Consisting Solely of Acrylamide Units

Herein, we report a method to synthesize a series of alternating copolymers that consist exclusively of acrylamide units. Crucial to realizing this polymer synthesis is the design of a divinyl monomer that contains acrylate and acrylamide moieties connected by two activated ester bonds. This design, which is based on the reactivity ratio of the embedded vinyl groups, allows a “selective” cyclopolymerization, wherein the intramolecular and intermolecular propagation are repeated alternately under dilute conditions. The addition of an amine to the resulting cyclopolymers afforded two different acryl amide units, i.e., an amine-substituted acryl amide and a 2-hydroxy-ethyl-substituted acryl amide in alternating sequence. Using this method, we could furnish ten types of alternating copolymers; some of these exhibit unique properties in solution and in the bulk, which are different from those of the corresponding random copolymers, and we attributed the differences to the alternating sequence.